Hybrid vehicle

ABSTRACT

A hybrid vehicle includes: an engine; first and second rotating electric machines; a connection/disconnection mechanism; a power storage device; and a control device. Further, when an acceleration request occurs during EV traveling mode, the control device controls, when determining that a predetermined acceleration smaller than a requested acceleration and corresponding to a vehicle speed cannot be generated by torque output by the second rotating electric machine, the torque output by the second rotating electric machine so as to generate an acceleration less than the predetermined acceleration while controlling the torque by the engine and torque by the first rotating electric machine, and when determining that the predetermined acceleration cannot be generated by the torque output by the second rotating electric machine, controls the torque output by the second rotating electric machine so as to generate the acceleration equal to or greater than the predetermined acceleration.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and incorporates by referencethe entire contents of Japanese Patent Application No. 2020-138189 filedin Japan on Aug. 18, 2020.

BACKGROUND

The present disclosure relates to a hybrid vehicle.

Japanese Laid-open Patent Publication No. 2019-142365 discloses a hybridvehicle including an engine, a first motor coupled to the engine, aclutch that selectively connects and disconnects a power transmissionpath between the engine and the first motor, and driving wheels, and asecond motor coupled to the driving wheels in such a manner as to beable to transmit power. This hybrid vehicle is capable of travelingbased on a required driving force by selecting either an EV travelingmode in which the clutch is disengaged to disconnect the engine from thepower transmission path to travel using the second motor as a drivingforce source or a parallel traveling mode in which the clutch is engagedto connect the engine to the power transmission path to travel using theengine and the second motor as driving force sources.

SUMMARY

There is a need for providing a hybrid vehicle capable of generating apredetermined acceleration at an early stage from a time when anacceleration request occurs

According to an embodiment, A hybrid vehicle includes: an engine; afirst rotating electric machine arranged on a power transmission pathfrom the engine to wheels and on an output side of the engine and havinga function of generating electricity by being driven by receiving atleast torque output by the engine; a connection/disconnection mechanismto selectively connect and disconnect the power transmission path; asecond rotating electric machine coupled to the wheels in such a manneras to be able to transmit power; a power storage device connected to thefirst rotating electric machine and the second rotating electricmachine; and a control device to control the engine, the first rotatingelectric machine, the second rotating electric machine, and theconnection/disconnection mechanism, in which the hybrid vehicle travelsby selecting any one of: an EV traveling mode to travel by stopping theengine to drive the wheels by torque output by the second rotatingelectric machine; a parallel traveling mode to travel by operating theengine while the power transmission path is connected by theconnection/disconnection mechanism to drive the wheels by the torqueoutput by the engine and the torque output by the second rotatingelectric machine; and a series traveling mode to travel by operating theengine while the power transmission path is disconnected by theconnection/disconnection mechanism to drive the first rotating electricmachine by the torque output by the engine to generate electricity andto drive the wheels by the torque output by the second rotating electricmachine. Further, when an acceleration request occurs during travelingin the EV traveling mode, the control device controls, when determiningthat a predetermined acceleration smaller than a requested accelerationand corresponding to a vehicle speed is not able to be generated by thetorque output by the second rotating electric machine, the torque outputby the second rotating electric machine in such a manner as to generatean acceleration less than the predetermined acceleration whilecontrolling the torque output by the engine and torque output by thefirst rotating electric machine, and when determining that thepredetermined acceleration is able to be generated by the torque outputby the second rotating electric machine, controls the torque output bythe second rotating electric machine in such a manner as to generate theacceleration equal to or greater than the predetermined acceleration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating a power train of a hybridvehicle according to an embodiment;

FIG. 2 is a diagram illustrating an example of a predetermined functionrepresenting the relationship between vehicle speed V and accelerationG0;

FIG. 3 is a diagram illustrating an example of a map representing therelationship between the vehicle speed V and the acceleration G0;

FIG. 4A is a diagram illustrating an example of a determinationcriterion for determining whether acceleration G0 can be output when theelectric power of a second rotating electric machine required togenerate the acceleration G0 is greater than the electric power requiredfor the maximum output of the second rotating electric machine;

FIG. 4B is a diagram illustrating an example of a determinationcriterion for determining whether the acceleration G0 can be output whenthe electric power required for the maximum output of the secondrotating electric machine is greater than the electric power of thesecond rotating electric machine required to generate the accelerationG0;

FIG. 5 is a timing chart illustrating an example of acceleration controlby a control pattern A;

FIG. 6 is a timing chart illustrating an example of acceleration controlby a control pattern B;

FIG. 7 is a timing chart illustrating an example of acceleration controlby a control pattern C; and

FIG. 8 is a flowchart illustrating an example of acceleration controlfrom traveling in an EV traveling mode of a hybrid vehicle under thecontrol of an ECU.

DETAILED DESCRIPTION

In the related art, when an acceleration request occurs during drivingin the EV traveling mode to accelerate the vehicle, it is conceivablethat the clutch is engaged to shift to the parallel traveling mode toaccelerate the vehicle using not only the torque output by the motor butalso the torque output by the engine. However, the responsiveness of thetorque output by the engine is generally slower than that by the motor,and a driver feels less acceleration. On the other hand, the feeling ofacceleration received by a driver depends not on the time from theoccurrence of the acceleration request to the generation of therequested acceleration according to the accelerator opening but on thetime from the occurrence of the acceleration request to the time whenthe minimum acceleration felt by the driver is exceeded.

Hereinafter, an embodiment of a hybrid vehicle according to the presentdisclosure will be described. Note that, the present disclosure is notlimited to the following embodiment.

FIG. 1 is a diagram schematically illustrating a power train of a hybridvehicle according to an embodiment. A hybrid vehicle 1 illustrated inFIG. 1 includes an engine (ENG) 2, a first rotating electric machine(MG1) 3, and a second rotating electric machine (MG2) 4 as powersources. In addition, the hybrid vehicle 1 according to the embodimentincludes, as other main component elements, a power control unit (PCU)5, a battery 6 as a power storage device, a clutch 7, an electroniccontrol unit (ECU) 8 as a control device, an output shaft 11, an outputshaft 12, an input shaft 13, a rear propeller shaft 14, a reardifferential gear 15, rear drive shafts 21R, rear wheels 22R, a frontpropeller shaft 16, a front differential gear 17, front drive shafts21F, front wheels 22F, a vehicle speed sensor 31, and an acceleratoropening sensor 32.

The engine 2 is, for example, an internal combustion engine, such as agasoline engine, a diesel engine or the like, and is configured in sucha manner that operating states, such as output adjustment, start, stopand the like, are electrically controlled.

The first rotating electric machine 3, the clutch 7, and the secondrotating electric machine 4 are arranged in order on the output side ofthe engine 2 and on the same axis as the engine 2.

The first rotating electric machine 3 is coupled to the output shaft 11of the engine 2 and has a function as a generator that generateselectricity by being driven by receiving the engine torque output by theengine 2 and a function as an electric motor that outputs rotaryelectric torque by being driven by supplied electric power. That is, thefirst rotating electric machine 3 is a motor generator having a powergeneration function and is implemented by, for example, a permanentmagnet type synchronous motor, an induction motor or the like. Inaddition, the first rotating electric machine 3 is connected to thebattery 6 via the PCU 5. Thus, the first rotating electric machine 3 canbe driven as a generator, and the electric power generated at that timecan be stored in the battery 6 or supplied to the second rotatingelectric machine 4. Furthermore, the electric power stored in thebattery 6 can be used to drive the first rotating electric machine 3 tooutput torque.

The clutch 7 is a connection/disconnection mechanism that selectivelyconnects and disconnects the power transmission path between the engine2 and the first rotating electric machine 3, and the rear wheels and isa hydraulic friction engagement device. The clutch 7 includes adrive-side friction plate coupled to the output shaft 12 of the firstrotating electric machine 3 and a driven-side friction plate coupled tothe input shaft 13 of the second rotating electric machine 4. Then, thefriction plates come into contact with each other to be in an engagedstate as the oil pressure supplied from an oil pump (not illustrated) isincreased, and the power transmission path between the engine 2 and thefirst rotating electric machine 3, and the rear wheels 22R is connected.In addition, the friction plates are separated from each other to be ina released state as the oil pressure is lowered, and the powertransmission path between the engine 2 and the first rotating electricmachine 3, and the rear wheels 22R is disconnected. Note that, theclutch 7 can be implemented by a multi-plate clutch in which a pluralityof drive-side friction plates and a plurality of driven-side frictionplates are provided and each drive-side friction plate and eachdriven-side friction plate are alternately arranged.

In the present embodiment, the clutch 7 is provided as aconnection/disconnection mechanism that selectively connects anddisconnects the power transmission path between the engine 2 and thefirst rotating electric machine 3, and the rear wheels 22R, but theconnection/disconnection mechanism is not limited thereto. For example,the connection/disconnection mechanism is only required to beimplemented by providing at least one of a clutch, a torque converter,and a transmission to selectively connect and disconnect the powertransmission path between the engine 2 and the first rotating electricmachine 3, and the rear wheels 22R in such a manner as to operate eachof the engine 2 and the first rotating electric machine 3 at anindependent rotation speed.

The second rotating electric machine 4 is coupled to the left and rightrear wheels in such a manner as to be able to transmit power. The secondrotating electric machine 4 has a function as a prime mover that outputsmotor torque by being driven by supplied electric power and a functionas a generator that generates electricity by being driven by receivingtorque from the outside. That is, the second rotating electric machine 4is, similarly to the first rotating electric machine 3, a motorgenerator having a power generation function and is implemented by, forexample, a permanent magnet type synchronous motor, an induction motoror the like. The second rotating electric machine 4 is connected to thebattery 6 via the PCU 5, and the second rotating electric machine 4 canbe driven by electricity from the battery 6 to output motor torque. Inaddition, since the second rotating electric machine 4 is coupled to therear wheels in such a manner as to be able to transmit power, the secondrotating electric machine 4 is driven as a generator by the torquetransmitted from the rear wheels, and the electric power generatedthereby can be stored in the battery 6. Furthermore, the first rotatingelectric machine 3 and the second rotating electric machine 4 areconnected to each other via the PCU 5 in such a manner that electricpower can be exchanged with each other, and the electricity generated bythe first rotating electric machine 3 can be directly supplied to thesecond rotating electric machine 4 in order for the second rotatingelectric machine 4 to output motor torque.

The rotor shaft of the second rotating electric machine 4 is coupled tothe rear propeller shaft 14. A rear propeller shaft 14 extends rearwardfrom the second rotating electric machine 4 in the front-rear directionof the hybrid vehicle 1. The rear propeller shaft 14 is coupled to therear differential gear 15. The rear differential gear 15 is coupled tothe left and right rear wheels (driving wheels) 22R via the left andright rear drive shafts 21R.

The ECU 8 is implemented by, for example, a microcomputer as a main bodyand is configured to perform calculation using input data or data storedin advance, to output the result of the calculation as a control commandsignal, and to control the engine 2, the PCU 5, and the like. The datainput to the ECU 8 is data from various sensors, such as the vehiclespeed sensor 31, the accelerator opening sensor 32 and the like, andswitches or from other systems.

Note that, the hybrid vehicle 1 according to the embodiment may beconfigured, as illustrated by a broken line in FIG. 1, by arranging thesecond rotating electric machine 4 on the vehicle front side to transmitthe torque output by the second rotating electric machine 4 to the leftand right front wheels 22F via the front propeller shaft 16, the frontdifferential gear 17, and the left and right front drive shafts 21F insuch a manner as to rotationally drive the left and right front wheels22F.

The hybrid vehicle 1 according to the embodiment is capable of travelingby setting any one of a plurality of traveling modes of an EV travelingmode, a series traveling mode, and a parallel traveling mode.

The EV traveling mode is a traveling mode to drive the hybrid vehicle 1by the motor torque output by the second rotating electric machine 4while the clutch 7 is released and the engine 2 and the first rotatingelectric machine 3 are stopped.

The series traveling mode is a traveling mode for the hybrid vehicle 1to travel by the motor torque of the second rotating electric machine 4by operating the engine 2 while the clutch 7 is released, driving thefirst rotating electric machine 3 by the engine 2 to generateelectricity, and driving the second rotating electric machine 4 by theelectric power generated by the first rotating electric machine 3.

The parallel traveling mode is a traveling mode for the hybrid vehicle 1to travel by the engine torque and the motor torque of the secondrotating electric machine 4 by operating the engine 2 while the clutch 7is engaged. In this parallel traveling mode, the hybrid vehicle 1 can bedriven by the motor torque output by the first rotating electric machine3 in addition to the engine torque and the motor torque of the secondrotating electric machine 4. In addition, in the parallel travelingmode, the reaction torque against the target engine torque is controlledto be output by the first rotating electric machine 3. In this case,regenerative control for causing the first rotating electric machine 3to function as a generator can be performed.

In the EV traveling mode, the series traveling mode, and the paralleltraveling mode, regenerative control is performed to cause the secondrotating electric machine 4 to function as a generator duringdeceleration or the like, and the electric power generated thereby canbe stored in the battery 6.

Here, in a hybrid vehicle, requested acceleration G is generally desiredto be generated immediately in response to a driver's accelerationrequest. However, during acceleration from traveling in the EV travelingmode, the driver feels less acceleration due to the time lag from theacceleration request to the engine start. The feeling of large time lagreceived by the driver depends not on the time from the occurrence ofthe acceleration request to the generation of the requested accelerationG according to the accelerator opening but on the time from theoccurrence of the acceleration request to the time when the minimumacceleration G0 that is smaller than the requested acceleration G andfelt by the driver is exceeded. For this reason, in the hybrid vehicle 1according to the embodiment, the ECU 8 is capable of performingacceleration control to generate the minimum acceleration G0 felt by thedriver at an early stage from a time when an acceleration request occursat the time when the acceleration request occurs during traveling in theEV traveling mode.

FIG. 2 is a diagram illustrating an example of a predetermined functionrepresenting the relationship between the vehicle speed V and theacceleration G0. FIG. 3 is a diagram illustrating an example of a maprepresenting the relationship between the vehicle speed V and theacceleration G0.

The minimum acceleration G0 felt by the driver is smaller than therequested acceleration G according to the accelerator opening, is, forexample, a predetermined acceleration corresponding to the vehicle speedV at the time of the acceleration request (the initial vehicle speedbefore acceleration), and tends to become greater as the vehicle speed Vat the time of the acceleration request (the initial vehicle speedbefore acceleration) is greater. Thus, in the present embodiment, theacceleration G0 with respect to the vehicle speed V is defined by, forexample, a linear function (the linear expression of the vehicle speedV) of G0=AV+B (where, A and B are constants), which is a predeterminedfunction representing the relationship between the vehicle speed V andthe acceleration G0, as illustrated in FIG. 2 or by a map indicating therelationship between the vehicle speed V and the acceleration G0 asillustrated in FIG. 3 in order to set the acceleration G0 used for theacceleration control.

In the hybrid vehicle 1 according to the embodiment, when determiningthat the acceleration G0 cannot be generated by the torque output by thesecond rotating electric machine 4 during traveling in the EV travelingmode, the ECU 8 controls the torque output by the second rotatingelectric machine 4 in such a manner as to generate acceleration lessthan the acceleration G0 while controlling the first rotating electricmachine 3 and the engine 2. On the other hand, when determining that theacceleration G0 can be generated using the torque output by the secondrotating electric machine 4 during traveling in the EV traveling mode,the ECU 8 controls the torque output by the second rotating electricmachine 4 in such a manner as to generate acceleration equal to orgreater than the acceleration G0 using the second rotating electricmachine 4.

In addition, when the electric power required for the maximum output ofthe second rotating electric machine 4 or the electric power suppliedfrom the battery 6 and the first rotating electric machine 3 to thesecond rotating electric machine 4 is less than the electric power ofthe second rotating electric machine 4 required to generate theacceleration G0, the ECU 8 determines that the acceleration G0 cannot begenerated by the torque output by the second rotating electric machine4.

Furthermore, when the electric power supplied from the battery 6 and thefirst rotating electric machine 3 to the second rotating electricmachine 4 or the electric power supplied from the battery 6 alone to thesecond rotating electric machine 4 is equal to or greater than theelectric power of the second rotating electric machine 4 required togenerate the acceleration G0, the ECU 8 determines that the accelerationG0 can be generated using the torque output by the second rotatingelectric machine 4.

FIG. 4A is a diagram illustrating an example of a determinationcriterion for determining whether the acceleration G0 can be output whenthe electric power of the second rotating electric machine 4 required togenerate the acceleration G0 is greater than the electric power requiredfor the maximum output of the second rotating electric machine 4. InFIG. 4A, W_(batt) is the maximum output electric power that can besupplied from the battery 6 to the second rotating electric machine 4.In FIG. 4A, W_(MG2) is the electric power required for the maximumoutput of the second rotating electric machine 4. In addition, in FIG.4A, W_(G0) is the electric power of the second rotating electric machine4 required to generate the acceleration G0.

In FIG. 4A, “No. 1” indicates that the maximum output electric powerW_(batt) that can be supplied from the battery 6 to the second rotatingelectric machine 4 is smaller than the electric power W_(MG2) requiredfor the maximum output of the second rotating electric machine 4 and theelectric power W_(G0) of the second rotating electric machine 4 requiredto generate the acceleration G0. In FIG. 4A, “No. 2” indicates that themaximum output electric power W_(batt) that can be supplied from thebattery 6 to the second rotating electric machine 4 is greater than theelectric power W_(MG2) required for the maximum output of the secondrotating electric machine 4 and is smaller than the electric powerW_(G0) of the second rotating electric machine 4 required to generatethe acceleration G0. In FIG. 4A, “No. 3” indicates that the maximumoutput electric power W_(batt) that can be supplied from the battery 6to the second rotating electric machine 4 is greater than the electricpower W_(MG2) required for the maximum output of the second rotatingelectric machine 4 and the electric power W_(G0) of the second rotatingelectric machine 4 required to generate the acceleration G0.

As illustrated in FIG. 4A, in any of the cases of “No. 1” to “No. 3”,the electric power W_(G0) of the second rotating electric machine 4required to generate the acceleration G0 is greater than the electricpower W_(MG2) required for the maximum output of the second rotatingelectric machine 4, regardless of the maximum output electric powerW_(batt) that can be supplied from the battery 6 to the second rotatingelectric machine 4. Thus, the ECU 8 determines that the acceleration G0cannot be generated by the torque output by the second rotating electricmachine 4 (determination A) and selects a control pattern A describedlater with reference to FIG. 5.

FIG. 4B is a diagram illustrating an example of a determinationcriterion for determining whether the acceleration G0 can be output whenthe electric power W_(MG2) required for the maximum output of the secondrotating electric machine 4 is greater than the electric power W_(G0) ofthe second rotating electric machine 4 required to generate theacceleration G0. In FIG. 4B, W_(MG1) is the electric power of themaximum electric power generation amount of the first rotating electricmachine 3. In FIG. 4B, W_(batt) is the maximum output electric powerthat can be supplied from the battery 6 to the second rotating electricmachine 4. In FIG. 4B, W_(MG2) is the electric power required for themaximum output of the second rotating electric machine 4. In FIG. 4B,W_(G0) is the electric power of the second rotating electric machine 4required to generate the acceleration G0.

In FIG. 4B, “No. 4” indicates that the electric power supplied from thebattery 6 and the first rotating electric machine 3 to the secondrotating electric machine 4 (W_(batt)+W_(MG1)) obtained by adding themaximum output electric power W_(batt) that can be supplied from thebattery 6 to the second rotating electric machine 4 to the electricpower W_(MG1) of the maximum electric power generation amount of thefirst rotating electric machine 3 is smaller than the electric powerW_(G0) of the second rotating electric machine 4 required to generatethe acceleration G0 and the electric power W_(MG2) required for themaximum output of the second rotating electric machine 4.

As illustrated in FIG. 4B, in the case of “No. 4”, the electric power(W_(batt)+W_(MG1)) supplied from the battery 6 and the first rotatingelectric machine 3 to the second rotating electric machine 4 is lessthan the electric power of the second rotating electric machine 4required to generate the acceleration G0. Thus, the ECU 8 determinesthat the acceleration G0 cannot be generated by the torque output by thesecond rotating electric machine 4 (determination A) and selects acontrol pattern A described later with reference to FIG. 5.

In FIG. 4B, “No. 5” indicates that the electric power supplied from thebattery 6 and the first rotating electric machine 3 to the secondrotating electric machine 4 (W_(batt)+W_(MG1)) obtained by adding themaximum output electric power W_(batt) that can be supplied from thebattery 6 to the second rotating electric machine 4 to the electricpower W_(MG1) of the maximum electric power generation amount of thefirst rotating electric machine 3 is greater than the electric powerW_(G0) of the second rotating electric machine 4 required to generatethe acceleration G0 and is smaller than the electric power W_(MG2)required for the maximum output of the second rotating electric machine4.

As illustrated in FIG. 4B, in the case of “No. 5”, the electric power(W_(batt)+W_(MG1)) supplied from the battery 6 and the first rotatingelectric machine 3 to the second rotating electric machine 4 is equal toor greater than the electric power W_(G0) of the second rotatingelectric machine 4 required to generate the acceleration G0. Thus, theECU 8 determines that the acceleration G0 can be generated by the torqueoutput by the second rotating electric machine 4 using the electricpower (W_(batt)+W_(MG1)) supplied from the battery 6 and the firstrotating electric machine 3 to the second rotating electric machine 4(determination B) and selects a control pattern B described later withreference to FIG. 6.

In FIG. 4B, “No. 6” indicates that the maximum output electric powerW_(batt) that can be supplied from the battery 6 to the second rotatingelectric machine 4 is greater than the electric power W_(G0) of thesecond rotating electric machine 4 required to generate the accelerationG0 and is smaller than the electric power W_(MG2) required for themaximum output of the second rotating electric machine 4. In FIG. 4B,“No. 7” indicates that the maximum output electric power W_(batt) thatcan be supplied from the battery 6 to the second rotating electricmachine 4 is greater than the electric power W_(G0) of the secondrotating electric machine 4 required to generate the acceleration G0 andthe electric power W_(MG2) required for the maximum output of the secondrotating electric machine 4.

As illustrated in FIG. 4B, in the cases of “No. 6” and “No. 7”, themaximum output electric power W_(batt) that can be supplied from thebattery 6 to the second rotating electric machine 4 is equal to orgreater than the electric power W_(G0) of the second rotating electricmachine 4 required to generate the acceleration G0. Thus, the ECU 8determines that the acceleration G0 can be generated by the torqueoutput by the second rotating electric machine 4 using the electricpower from the battery 6 alone (determination C) and selects a controlpattern C described later with reference to FIG. 7.

FIG. 5 is a timing chart illustrating an example of acceleration controlby the control pattern A. In FIG. 5, the MG1 torque is the torque outputby the first rotating electric machine 3, the MG2 torque is the torqueoutput by the second rotating electric machine 4, and the G0 thresholdis the threshold of the acceleration G0. The same applies to FIGS. 6 and7.

In the acceleration control by the control pattern A, shifting from theEV traveling mode to the parallel traveling mode is prioritized togenerate the minimum acceleration G0 felt by the driver at an earlystage from a time when an acceleration request occurs.

First, in the control pattern A, the second rotating electric machine 4outputs, at the timing when the acceleration request occurs, the torquefor maintaining the vehicle speed. In addition, at the timing when theacceleration request occurs, the remaining electric power of the battery6 except for that to be used by the second rotating electric machine 4is supplied to the first rotating electric machine 3, and the torque isoutput from the first rotating electric machine 3 to the engine 2 tostart (crank) the engine 2 by the first rotating electric machine 3.Then, by keeping outputting the torque from the first rotating electricmachine 3 to the engine 2 after the engine is ignited to assist theincrease in the engine speed, the time until the engine speed reachesthe clutch engagement speed at which the clutch 7 is engaged is reduced.Then, the clutch 7 is engaged at the timing when the engine speedreaches the clutch engagement speed, the vehicle is accelerated in theparallel traveling mode to generate the acceleration G0. Furthermore,the vehicle is continuously accelerated in the parallel traveling modeafter reaching the acceleration G0 to the requested acceleration.

FIG. 6 is a timing chart illustrating an example of acceleration controlby the control pattern B.

In the control pattern B, shifting from the EV traveling mode to theseries traveling mode is prioritized to generate the minimumacceleration G0 felt by the driver at an early stage from a time when anacceleration request occurs.

First, in the control pattern B, the second rotating electric machine 4outputs, at the timing when the acceleration request occurs, the torquefor maintaining the vehicle speed. In addition, at the timing when theacceleration request occurs, the remaining electric power of the battery6 except for that to be used by the second rotating electric machine 4is supplied to the first rotating electric machine 3, and the torque isoutput from the first rotating electric machine 3 to the engine 2 tostart (crank) the engine 2 by the first rotating electric machine 3.Then, after the engine is ignited, the first rotating electric machine 3is driven using a part of the engine torque to generate electricity forthe amount of electric power insufficient for the generation of theacceleration G0 by the second rotating electric machine 4. Then, theelectric power W_(G0) of the second rotating electric machine 4 requiredto generate the acceleration G0 is supplied to the second rotatingelectric machine 4 by adding the electric power generated by the firstrotating electric machine 3 to the electric power supplied from thebattery 6 to the second rotating electric machine 4, and the vehicle isaccelerated in the series traveling mode by increasing the torque outputby the second rotating electric machine 4 to generate the accelerationG0. Thereafter, while the acceleration G0 is maintained, the clutch 7 isengaged at the timing when the engine speed reaches the clutchengagement speed, and the vehicle is accelerated in the paralleltraveling mode to the requested acceleration.

In the control pattern B, the acceleration G0 can be generated earlierthan the control pattern A in which the acceleration G0 is generatedafter the increase in the engine speed and the clutch engagement.

FIG. 7 is a timing chart illustrating an example of acceleration controlby the control pattern C.

In the control pattern C, the generation of the acceleration G0 byaccelerating the vehicle in the EV traveling mode is prioritized togenerate the minimum acceleration G0 felt by the driver at an earlystage from a time when an acceleration request occurs.

First, in the control pattern C, the second rotating electric machine 4outputs, at the timing when the acceleration request occurs, the torquerequired to generate the acceleration G0 by supplying the electric powerW_(G0) of the second rotating electric machine 4 required to generatethe acceleration G0 from the battery 6 to the second rotating electricmachine 4, and the vehicle is accelerated in the EV traveling mode togenerate the acceleration G0. At that time, the torque output by thesecond rotating electric machine 4 is limited to the minimum necessaryamount for generating the acceleration G0. In addition, at the timingwhen the acceleration request occurs, the remaining electric power ofthe battery 6 except for that to be used by the second rotating electricmachine 4 is supplied to the first rotating electric machine 3, and thetorque is output from the first rotating electric machine 3 to theengine 2 to start (crank) the engine 2 by the first rotating electricmachine 3. Then, by keeping outputting the torque from the firstrotating electric machine 3 to the engine 2 after the engine is ignitedto assist the increase in the engine speed, the time until the enginespeed reaches the clutch engagement speed is reduced. Then, the clutch 7is engaged at the timing when the engine speed reaches the clutchengagement speed, the vehicle is accelerated in the parallel travelingmode to the requested acceleration.

FIG. 8 is a flowchart illustrating an example of acceleration controlfrom traveling in the EV traveling mode of the hybrid vehicle 1 underthe control of the ECU 8.

First, the ECU 8 determines whether there is an acceleration requestfrom the driver based on the accelerator opening from the acceleratoropening sensor 32 (step S1). When determining that there is noacceleration request from the driver (No in step S1), the ECU 8 repeatsthe determination in step S1 until an acceleration request from thedriver occurs.

On the other hand, when determining that an acceleration request fromthe driver occurs (Yes in step S1), the ECU 8 determines whether toperform acceleration feeling effect processing (step S2). Theacceleration feeling effect processing is determined, for example, to beperformed when the requested acceleration exceeds a predeterminedthreshold or not to be performed when the requested acceleration isequal to or less than the predetermined threshold. The predeterminedthreshold is defined by, for example, a map based on the current vehiclespeed or the like. Alternatively, the predetermined threshold may be setaccording to the driving style of each driver by machine learning thedriving state of each driver.

When determining that the acceleration feeling effect processing is tobe performed (Yes in step S2), the ECU 8 determines whether theacceleration G0 can be output (step S3). Note that, the determination asto whether the acceleration G0 can be output is performed according to,for example, the determination criteria explained with reference toFIGS. 4A and 4B.

When the determination as to whether the acceleration G0 can be outputis the determination A (determination A in step S3), the ECU 8 performsthe acceleration control by the control pattern A described withreference to FIG. 5 (step S4) and terminates a series of controls.Alternatively, when the determination as to whether the acceleration G0can be output is the determination B (determination B in step S3), theECU 8 performs the acceleration control by the control pattern Bdescribed with reference to FIG. 6 (step S5) and terminates a series ofcontrols. Alternatively, when the determination as to whether theacceleration G0 can be output is the determination C (determination C instep S3), the ECU 8 performs the acceleration control by the controlpattern C described with reference to FIG. 7 (step S6) and terminates aseries of controls.

When determining that the acceleration feeling effect processing is notperformed in step S2 (No in step S2), the ECU 8 performs normalacceleration control (step S7) and terminates a series of controls. Thenormal acceleration control is, for example, a control for acceleratingthe vehicle to the requested acceleration while the EV traveling mode ismaintained.

As described above, the hybrid vehicle 1 according to the embodiment cangenerate the minimum acceleration G0 felt by the driver at an earlystage from a time when an acceleration request occurs in considerationof the output responsiveness of the engine 2 and the second rotatingelectric machine 4.

A hybrid vehicle according to the present disclosure has an effect thata predetermined acceleration can be generated at an early stage from atime when an acceleration request occurs, in consideration of the outputresponsiveness of an engine and a second rotating electric machine.

According to an embodiment, it is possible to generate a minimumacceleration felt by a driver at an early stage from a time when anacceleration request occurs, in consideration of the outputresponsiveness of the engine and the second rotating electric machine.

According to an embodiment, it is possible to preferentially shift fromthe EV traveling mode to the parallel traveling mode to perform adetermination to generate the predetermined acceleration at an earlystage.

According to an embodiment, it is possible to preferentially shift fromthe EV traveling mode to the parallel traveling mode to generate thepredetermined acceleration at an early stage.

According to an embodiment, it is possible to preferentially shift fromthe EV traveling mode to the series traveling mode to perform adetermination to generate the predetermined acceleration at an earlystage.

According to an embodiment, it is possible to preferentially shift fromthe EV traveling mode to the series traveling mode to generate thepredetermined acceleration at an early stage.

According to an embodiment, it is possible to preferentially generatethe predetermined acceleration by accelerating the vehicle in the EVtraveling mode to perform a determination to generate the predeterminedacceleration at an early stage.

According to an embodiment, it is possible to preferentially generatethe predetermined acceleration by accelerating the vehicle in the EVtraveling mode to generate the predetermined acceleration at an earlystage.

According to an embodiment, it is possible to appropriately set thepredetermined acceleration that tends to increase as the vehicle speedincreases.

According to an embodiment, it is possible to appropriately set thepredetermined acceleration that tends to increase as the vehicle speedincreases.

Although the disclosure has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

What is claimed is:
 1. A hybrid vehicle comprising: an engine; a firstrotating electric machine arranged on a power transmission path from theengine to wheels and on an output side of the engine and having afunction of generating electricity by being driven by receiving at leasttorque output by the engine; a connection/disconnection mechanismconfigured to selectively connect and disconnect the power transmissionpath; a second rotating electric machine coupled to the wheels in such amanner as to be able to transmit power; a power storage device connectedto the first rotating electric machine and the second rotating electricmachine; and a control device configured to control the engine, thefirst rotating electric machine, the second rotating electric machine,and the connection/disconnection mechanism, the hybrid vehicle beingconfigured to travel by selecting any one of: an EV traveling mode totravel by stopping the engine to drive the wheels by torque output bythe second rotating electric machine; a parallel traveling mode totravel by operating the engine while the power transmission path isconnected by the connection/disconnection mechanism to drive the wheelsby the torque output by the engine and the torque output by the secondrotating electric machine; and a series traveling mode to travel byoperating the engine while the power transmission path is disconnectedby the connection/disconnection mechanism to drive the first rotatingelectric machine by the torque output by the engine to generateelectricity and to drive the wheels by the torque output by the secondrotating electric machine, wherein when an acceleration request occursduring traveling in the EV traveling mode, the control device isconfigured to control, when determining that a predeterminedacceleration smaller than a requested acceleration and corresponding toa vehicle speed is not able to be generated by the torque output by thesecond rotating electric machine, the torque output by the secondrotating electric machine in such a manner as to generate anacceleration less than the predetermined acceleration while controllingthe torque output by the engine and torque output by the first rotatingelectric machine, and when determining that the predeterminedacceleration is able to be generated by the torque output by the secondrotating electric machine, control the torque output by the secondrotating electric machine in such a manner as to generate theacceleration equal to or greater than the predetermined acceleration. 2.The hybrid vehicle according to claim 1, wherein the control device isconfigured to determine, when electric power required for a maximumoutput of the second rotating electric machine or electric powersupplied from the power storage device and the first rotating electricmachine to the second rotating electric machine is less than electricpower of the second rotating electric machine required to generate thepredetermined acceleration, that the predetermined acceleration is notable to be generated by the torque output by the second rotatingelectric machine.
 3. The hybrid vehicle according to claim 2, whereinthe predetermined acceleration is generated by the torque output by theengine and the torque output by the second rotating electric machineafter shifting from the EV traveling mode to the parallel travelingmode.
 4. The hybrid vehicle according to claim 1, wherein the controldevice is configured to determine, when electric power supplied from thepower storage device and the first rotating electric machine to thesecond rotating electric machine is equal to or greater than electricpower of the second rotating electric machine required to generate thepredetermined acceleration, that the predetermined acceleration is ableto be generated by the torque output by the second rotating electricmachine.
 5. The hybrid vehicle according to claim 4, wherein thepredetermined acceleration is generated by the torque output by thesecond rotating electric machine using the electric power supplied fromthe power storage device and the first rotating electric machine to thesecond rotating electric machine after shifting from the EV travelingmode to the series traveling mode.
 6. The hybrid vehicle according toclaim 1, wherein the control device is configured to determine, whenelectric power supplied from the power storage device alone to thesecond rotating electric machine is equal to or greater than electricpower of the second rotating electric machine required to generate thepredetermined acceleration, that the predetermined acceleration is ableto be generated by the torque output by the second rotating electricmachine.
 7. The hybrid vehicle according to claim 6, wherein thepredetermined acceleration is generated by the torque output by thesecond rotating electric machine in the EV traveling mode.
 8. The hybridvehicle according to claim 1, wherein the control device is configuredto set the predetermined acceleration using a predetermined functionrepresenting relationship between the vehicle speed and thepredetermined acceleration.
 9. The hybrid vehicle according to claim 1,wherein the control device is configured to set the predeterminedacceleration using a map representing relationship between the vehiclespeed and the predetermined acceleration.